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Biomedical subjects

F M Walker

Publications and source records attributed to F M Walker.

At least 19 recordsLinked to original sources
PubMed1998

Detection and localization by in situ molecular biology techniques and immunohistochemistry of hepatitis C virus in livers of chronically infected patients.

Hepatitis C virus (HCV) detection in the livers of chronically infected patients remains a debatable issue. We used immunohistochemistry, in situ hybridization (ISH) alone or after microwave heating with FITC-labeled probes, RT-PCR with unlabeled primers followed by ISH (RT-PCR-ISH), and in situ RT-PCR with FITC-labeled primers (in situ RT-PCRd) to localize the virus in 38 liver biopsy specimens from 21 chronically infected HCV patients treated with interferon-alpha (IFN-alpha). Biopsies were taken at the beginning and end of IFN-alpha treatment and 1 year later. Results were compared with that of HCV-PCR in serum. RT-PCR-ISH and in situ RT-PCRd showed HCV signal in all liver biopsies even in responders with seronegative HCV PCR. This signal was intranuclear, diffuse, or peripheral, in hepatocytes, bile ductule cells, and lymphocytes. Cytoplasmic signals were occasionally observed. Whereas the percentage of labeled hepatocytes remained constant, the number of labeled lymphoid follicles decreased after INF-alpha therapy. Immunohistochemistry resulted in the same pattern of positivity but it was weaker and inconstant. This study indicates the persistency of HCV latency in IFN-alpha responders 1 year after IFN-alpha treatment cessation, a finding that certainly deserves confirmation.

Animals↗
PubMed1992

Detection of gastrin mRNA in human antral mucosa and digestive endocrine tumors by in situ hybridization: a correlative study with immunocytochemistry and electron microscopy.

In gastrinomas, as well as in other endocrine tumors whose hormone overproduction is responsible for clinical syndromes, antibodies against the bioactive form(s) of hormones can fail to detect immunoreactivity. Moreover, tumor secretory granule morphology may fail to allow tumor type identification. The use of anti-pre-pro-gastrin antibodies has been proposed as an alternative to identify gastrinomas. The aim of the present study was to demonstrate that in situ detection of gastrin mRNA may represent another possibility. A 35S-labeled cDNA probe encoding the human gastrin pre-pro-hormone was used to localize gastrin gene transcripts in antral mucosa and digestive endocrine tumors from patients with a Zollinger-Ellison syndrome characterized by high serum gastrin levels. In situ hybridization was combined with light and electron microscopic immunostaining of the bioactive gastrin 17/34 form and morphological study of secretory granules. Gastrin mRNAs were detected in antral gastrin cells and in a variable proportion of tumor cells in all endocrine tumor studied. Transcript expression correlated well with immunohistochemical staining and granule ultrastructure for most of the tumors, and provided crucial evidence for identifying as gastrinomas two tumors with weak immunoreactivity and poorly granulated cells. Our data show that in situ hybridization is a sensitive method for gastrin mRNA detection and represents a valuable tool for the identification of gastrinomas.

Digestive System Neoplasms↗
PubMed1987

ACTH initiation of mammary secretion in pregnant goats is influenced by the stage of gestation and pre partum milking.

Pregnant goats were treated with ACTH by intramuscular injection (1 mg/d for 2 d) at various stages of pregnancy to investigate its effect on initiation of mammary secretion. ACTH stimulated lactose secretion and increased udder volume at or after 84 d of gestation, when compared with untreated controls. Treatment with ACTH between d 109 and 127 of gestation increased circulating plasma glucose concentration, mammary blood flow and mammary uptake of glucose which returned to pre injection levels 6 d after treatment. Arterial concentrations of progesterone were not affected by ACTH but mammary progesterone uptake increased 2-fold. Pre partum milking alone stimulated mammary secretion in eight of 13 goats. Subsequent treatment with ACTH resulted in no further change in the composition of the secretion but increase in yield was maintained. ACTH stimulated mammary secretion in those goats which did not respond to pre partum milking. It was concluded that ACTH initiated mammary secretion in pregnant goats by mechanisms which interact with the stimulation of milking but which are independent of circulating progesterone levels.

Adrenocorticotropic Hormone↗
PubMed1983

Pre-partum changes in the plasma concentrations of progesterone, relaxin, prostaglandin F-2 alpha and 13,14-dihydro-15-keto prostaglandin F-2 alpha in meclofenamic acid-treated sows.

The pre-partum plasma concentrations of progesterone, relaxin, PGF-2 alpha and 13,14-dihydro-15-keto PGF-2 alpha (PGFM) were determined in 6 sows treated with meclofenamic acid (5.0 mg/kg body wt daily, from Day 109 to Day 113 of pregnancy), and 2 sows which farrowed prematurely. The inhibition of PG synthesis with meclofenamic acid did not prevent either the decline in plasma progesterone or the release of relaxin. Three distinct stages in the progressive changes of the above hormones were apparent before parturition: (1) the gradual decline in the concentrations of progesterone from about 7 days pre partum to reach less than 4.5 ng/ml at farrowing; (2) a surge in relaxin levels (greater than 100 ng/ml) by 2 days pre partum; and (3) sharp increases in the concentrations of PGF-2 alpha and PGFM within 24 h of parturition. Maximal concentrations of PGF-2 alpha (greater than 0.5 ng/ml) and PGFM (greater than 20.0 ng/ml) occurred during farrowing. It is suggested that PG from an extra-ovarian source may not be responsible for initiating functional regression of the corpora lutea in the sow.

Animals↗
PubMed1981

Protein, prostaglandin and steroid synthesis in caruncular and intercaruncular endometrium of sheep before implantation.

The effect of the presence of a preimplantation embryo on protein concentration, rate of protein synthesis, beta-glucuronidase and acid phosphatase activities, steroid metabolism and prostaglandin F production in caruncular and intercaruncular tissue have been studied for sheep at Day 15 of pregnancy. The rate of protein synthesis in both tissues was greater in pregnant than in non-pregnant animals, although the difference was only significant in caruncular endometrium. The effect in caruncular tissue was mimicked in ovariectomized animals treated with oestradiol. Localized changes in the caruncular tissue were observed in respect of PGF with an increased tissue concentration, an enhanced basal release when the tissue was incubated in the presence of indomethacin, and a decreased net production. Maximum production of PGF in the 2 tissues was unaffected by the presence of an embryo but it was enhanced by oestradiol or progesterone treatment in intercaruncular tissue of ovariectomized ewes. beta-Glucuronidase and acid phosphatase activities and steroid metabolism were unaffected by pregnancy. However, in ovariectomized animals oestradiol treatment stimulated beta-glucuronidase activity in endometrium and myometrium. Progesterone treatment stimulated acid phosphatase activity in the intercaruncular endometrium. The results show that amongst several endometrial constituents investigated relatively few changes were detected by Day 15 post coitum, one day before definitive attachment. Those changes that did occur were associated with the dynamics of PGF production and the rate of protein synthesis, and were consistent with the production of a PGF binding component in caruncular endometrium which may be concerned with the protection of luteal function by redirection of uterine PGF production. Canonical variate analysis revealed that changes on Day 15 of pregnancy were mimicked most closely in caruncular tissue by treatment of ovariectomized ewes with oestradiol and progesterone, and in intercaruncular tissue by oestradiol treatment only.

Acid Phosphatase↗
PubMed1979

Changes in mammary function at the onset of lactation in the goat: correlation with hormonal changes.

1. Changes in mammary function and plasma hormone concentrations during late pregnancy and the onset of lactation have been studied in conscious goats.2. Mammary blood flow, oxygen consumption and glucose uptake increased markedly and significantly between 2 days and 0.5-1 day pre-partum.3. The increase in mammary glucose uptake was relatively greater than that of oxygen consumption or blood flow.4. The concentration of citrate in mammary secretion increased; the first significant change was apparent 0.5-1 day pre-partum but the main rise occurred after this time.5. It is concluded that the marked increase in mammary glucose uptake 0.5-1 day before parturition indicates the time of onset of copious milk secretion.6. The first significant increase in the concentration of unconjugated oestrogens in arterial plasma occurred 3 days pre-partum, whereas the first significant decrease in progesterone and increase in 13,14-dihydro-15-oxoprostaglandin F(2alpha) occurred 0.5-1 day pre-partum, thus coinciding with the mammary changes; there was also a peak in prolactin concentrations at the latter time.7. The hormonal changes are discussed in relation to current concepts of the initiation of parturition and the onset of copious milk secretion in this species. It is suggested that the fall in plasma progesterone concentrations triggers milk secretion at high rates.

Animals↗
PubMed1978

Antiluteolytic effect of the embryo.

In several mammalian species, prostaglandin F2 alpha (PGF2 alpha) released from the uterus causes corpus luteum regression, and thereby regulates the length of the oestrous cycle or pseudopregnancy. If the animal becomes pregnant, luteal regression must be prevented since ovarian progesterone is necessary for pregnancy maintenance during at least the first one-third of pregnancy. Evidence is presented that the guinea-pig conceptus produces an antiluteolytic factor which suppresses PGF2 alpha output from the uterus by preventing the increase in uterine PGF2 alpha-synthesizing capacity which occurs around the time of luteolysis. Experiments in unilaterally pregnant guinea-pigs, with either an intact or a transected sterile horn, indicate that this factor acts both locally systemically, though separation of the two uterine horns does greatly reduce its effect on the sterile side. Oestradiol administered during early pregnancy induces abortion, which is associated with a high PGF2 alpha-synthesizing capacity of the uterus. However, luteal regression does not take place while the conceptuses are in the uterus. Spontaneously aborting guinea-pigs behave similarly. The conceptus may therefore secrete a luteotrophic hormone as well. Luteal maintenance during early pregnancy in other species is discussed, since experiments on sheep indicate that the sheep embryo may also secrete an antiluteolytic factor.

Abortion, Spontaneous↗
PubMed1978

The metabolism of prostaglandins by the guinea-pig uterus with particular reference to corpus luteal maintenance in early pregnancy.

1 Homogenized lung tissue from day 15, pregnant and non-pregnant guinea-pig metabolized exogenous prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha) almost completely when incubated in Tyrode solution containing beta-nicotinamide adenine dinucleotide (NAD+). 2 Metabolism of PGE2 and PGF2alpha by homogenates of day 15, pregnant or non-pregnant, guinea-pig uteri was relatively low (8 to 20%) when incubated in Tyrode solution containing NAD+. 3 Day 15, guinea-pig conceptuses (placentae and embryos), homogenized and incubated in Tyrode solution containing NAD+, metabolized prostaglandins to a slightly greater extent (14 to 22%) than day 15, uterine tissue. 4 Addition of exogenous arachidonic acid to day 12 or day 15, pregnant, guinea-pig uterine homogenates in Tyrode solution did not increase the yield of PGF2alpha following incubation. 5 It is concluded that neither an increase in metabolism of PGF2alpha by the uterus and conceptus nor lack of precursor is responsible for the lower secretion of PGF2alpha from the day 15, pregnant, guinea-pig uterus when compared to the day 15, non-pregnant uterus.

Animals↗
PubMed1977

The metabolism of prostaglandins F2alpha and E2 by non-pregnant porcine endometrial and luteal tissue and early pregnant porcine endometrial tissue, luteal tissue and conceptuses in vitro.

Slices of porcine endometrium and corpus luteum from both early pregnant and non-pregnant sows and conceptuses from early pregnant sows were incubated with radioactive PGF2alpha and PGE2 and the degree of metabolism of the prostaglandins measured. Prostaglandins and a metabolites were separated by TLC, radioactive bands located with a Panax scanner and the radioactivity measured in a scintillation counter. Endometrial and luteal tissue from non-pregnant sows gave no significant metabolism at any stage of the oestrous cycle, and while similar tissue from pregnant sows metabolised both prostaglandins slightly, only the conceptuses gave any significant metabolism. The possible physiological significance of these results is discussed.

Animals↗
PubMed1977

The effect of cloprostenol on human luteal steroid and prostaglandin secretion in vitro.

1 Human luteal tissue slices from days 18, 21 and 25 of the menstrual cycle were superfused in vitro with Medium 199 alone or containing cloprostenol (1 microgram/ml). Concentrations of progesterone, oestradiol-17beta and prostaglandins F2alpha and E2 were determined in the superfusate samples. 2 Secretion of steroids and prostaglandins was maintained at an approximately constant level throughout the experiments (21 h in one case) when the tissue was perfused with M199 alone. 3 Superfusion with cloprostenol (1 microgram/ml) resulted in an initial depression of progesterone and oestradiol-17beta but this was not maintained, levels returning to control values or showing an increase, while superfusion with cloprostenol continued. Cloprostenol is not therefore considered to be luteolytic at this dose and under these conditions for human luteal tissue in vitro. 4 Superfusion with cloprostenol (1 microgram/ml) also resulted in a large stimulation of secretion of endogenous prostaglandin F2 alpha following a short lag phase. This stimulation was possibly due to the initial depression of progesterone secretion. A short-lived stimulation of prostaglandin E2 secretion was also observed. 5 The significance of the increase in prostaglandin E2 secretion and the interrelationships between the various changes observed with cloprostenol are difficult to interpret.

Corpus Luteum↗
PubMed1977

Effect of prostaglandin F-2alpha and uterine extracts on progesterone secretion in vitro by superfused pig corpora lutea.

Corpora lutea obtained from sows in the mid-luteal phase of the oestrous cycle were superfused with various doses of PGF-2alpha, uterine flushings or superfusates from endometrial strips. High doses of PGF-2alpha (1-5 microgram/ml) gave transient stimulation of progesterone secretion; lower doses (0.1-1.0 microgram/ml) inhibited secretion of the steroid, but to a maximum of 55% only and the secretion returned to control levels when superfusion with PGF-2alpha stopped. Uterine flushings from sows in the late luteal phase of the cycle were more effective than mid-cycle flushings in inhibiting progesterone secretion by the luteal tissue: maximal inhibition was 65% and progesterone secretion slowly returned to control levels when superfusion with the flushings was stopped. Superfusate from strips of uterine endometrium from sows in the late luteal phase of the cycle proved most effective in inhibiting progesterone secretion (greater than 90%) and gave a long-lasting inhibition which did not appear to be due to stimulation of PGF-2alpha secretion by the endometrium or corpus luteum.

Animals↗
PubMed1975

Progesterone, prostaglandin F2alpha, and oestradiol in the utero-ovarian venous plasma of non-pregnant and early, unilaterally pregnant guinea-pigs.

Levels of progesterone, prostaglandin F2alpha (PGF2alpha) and oestradiol in the utero-ovarian venous plasma of non-pregnant and early, unilaterally pregnant guinea-pigs were compared. Progesterone levels fell from day 12 to day 15 in the non-pregnant animals, while levels of PGF2alpha and oestradiol increased during this period. In contrast, in the pregnant guinea-pigs, progesterone levels remained high up to day 15 and PGF2alpha and oestradiol levels remained low in plasma from both the pregnant and non-pregnant sides. These findings support the hypothesis that the guinea-pig conceptus secretes an anti-luteolytic factor in early pregnancy, which reduces the amount of PGF2alpha produced by the uterus and released into the uterine veins and thereby allows luteal maintenance and continued progesterone secretion. Oestradiol, in the presence of progesterone, is regarded as the physiological stimulus for normal uterine PGF2alpha synthesis and release. Consequently, the inhibition of ovarian oestradiol secretion seen in early pregnancy is probably at least part of the mechanism by which the anti-luteolytic factor produced by the conceptus reduces PGF2alpha synthesis by and release from the uterus.

Animals↗